U.S. patent application number 12/626845 was filed with the patent office on 2010-06-03 for process and process line for the preparation of hydraulic fracturing fluid.
Invention is credited to Grant DeFosse, Lois McCorriston.
Application Number | 20100132949 12/626845 |
Document ID | / |
Family ID | 42221745 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132949 |
Kind Code |
A1 |
DeFosse; Grant ; et
al. |
June 3, 2010 |
PROCESS AND PROCESS LINE FOR THE PREPARATION OF HYDRAULIC
FRACTURING FLUID
Abstract
A process and process line is provided for preparing a
friction-reduced hydraulic fracturing fluid at a central location
which can be readily transported to an oil or gas well in a
formation at a well site, comprising: preparing a mixture of
polymer and water at the central location by shearing the polymer
in the water in a high shear environment to create the
friction-reduced hydraulic fracturing fluid; pumping the
friction-reduced hydraulic fracturing fluid through a series of
pumps and pipelines to the well site; and injecting the hydraulic
fracturing fluid into the oil or gas well at a pressure sufficient
to cause fracturing of the formation.
Inventors: |
DeFosse; Grant; (Calgary,
CA) ; McCorriston; Lois; (Calgary, CA) |
Correspondence
Address: |
BENNETT JONES LLP;C/O MS ROSEANN CALDWELL
4500 BANKERS HALL EAST, 855 - 2ND STREET, SW
CALGARY
AB
T2P 4K7
CA
|
Family ID: |
42221745 |
Appl. No.: |
12/626845 |
Filed: |
November 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12255478 |
Oct 21, 2008 |
|
|
|
12626845 |
|
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Current U.S.
Class: |
166/308.1 ;
166/90.1 |
Current CPC
Class: |
E21B 43/26 20130101;
E21B 43/267 20130101; E21B 19/00 20130101; E21B 21/062 20130101;
B01F 3/1271 20130101; B01F 3/1221 20130101; B01F 3/1228
20130101 |
Class at
Publication: |
166/308.1 ;
166/90.1 |
International
Class: |
E21B 43/26 20060101
E21B043/26; E21B 19/00 20060101 E21B019/00 |
Claims
1. A process for preparing a friction-reduced hydraulic fracturing
fluid at a central location which can be readily transported to an
oil or gas well in a formation at a well site, comprising:
preparing a mixture of polymer and water at the central location by
shearing the polymer in the water in a high shear environment to
create the friction-reduced hydraulic fracturing fluid; pumping the
friction-reduced hydraulic fracturing fluid through a series of
pumps and pipelines to the well site; and injecting the hydraulic
fracturing fluid into the gas well at a pressure sufficient to
cause fracturing of the formation.
2. The process as claimed in claim 1, further comprising adding
additional water to the friction-reduced hydraulic fracturing fluid
prior to pumping it to the well site.
3. The process as claimed in claim 1, further comprising adding an
additive to the friction-reduced hydraulic fracturing fluid prior
to pumping it to the remote well site.
4. The process as claimed in claim 3, wherein the additive is
selected from the group consisting of surfactants, acids, biocides,
H.sub.2S scavengers, scale inhibitors and O.sub.2 scavengers.
5. The process as claimed in claim 1, wherein the polymer is
selected from the group consisting of partially hydrolyzed
polyacrylamides, polyacrylamides and polymethacrylamides,
cross-linked polyacrylamides and cross-linked polymethacrylamides,
polyacrylic acid and polymethacrylic acid, polyacrylates, polymers
of N-substituted acrylamides, co-polymers of acrylamide with
another ethylenically unsaturated monomer co-polymerizable
therewith, 2-acrylamido-2-methylpropane sulfonic acid, polyvinyl
pyrollidones, guar, substituted guars, biopolymers such as xanthan
gum, welan gum and diutan gum, carboxymethyl cellulose, and other
mixtures of polymers.
6. The process as claimed in claim 1, further comprising: retaining
the friction-reduced hydraulic fracturing fluid in a surge tank
located at the well site prior to pumping it down the well.
7. The process as claimed in claim 1, further comprising: mixing
the friction-reduced hydraulic fracturing fluid with a proppant in
a blender located at the well site prior to pumping it down the
well.
8. The proppant as claimed in claim 7, wherein the proppant is
selected from the group consisting of sand grains, ceramics,
sintered bauxite, glass beads and plastic beads.
9. A process line for preparing a friction-reduced hydraulic
fracturing fluid at a central location for transport to an oil or
gas well at a well site, comprising: a water plant site having: a
water supply; a bulk polymer storage tank containing a supply of
polymer and a conveyer/auger at one end; a shearing mixer operably
associated with both the bulk polymer storage tank and the water
supply for receiving the polymer and mixing the polymer with
sufficient water to form a friction-reduced hydraulic fracturing
fluid; at least one pump for pumping the friction-reduced hydraulic
fracturing fluid though at least one pipeline to the well site; and
at least one fracturing pump located at the remote well site for
receiving the friction-reduced hydraulic fracturing fluid and
pumping it down the oil or gas well located at the well site.
10. The process line as claimed in claim 9, further comprising at
least two pumps for pumping the friction-reduced hydraulic
fracturing fluid though the at least one pipeline to the well
site.
11. The process line as claimed in claim 10, further comprising a
static mixer between the at least two pumps.
12. The process line as claimed in claim 9, further comprising a
surge tank located at the well site for retaining the
friction-reduced hydraulic fracturing fluid prior to pumping it
through the at least one fracturing pump.
13. The process line as claimed in claim 9, further comprising a
blender located at the well site for receiving the friction-reduced
hydraulic fracturing fluid and a proppant prior to pumping it
through the at least one fracturing pump.
14. A mobile hydraulic fracturing fluid preparation unit for
preparing hydraulic fracturing fluid for fracturing an oil or gas
well formation at a well site, comprising: a mobile trailer or skid
having situated thereon: a shearing mixer for receiving a polymer
from a bulk polymer storage tank and for receiving water from a
water source, said shearing mixer operable to mix the polymer with
sufficient water to hydrate the polymer; at least one pump for
receiving the hydrated polymer and additional water from the water
source to form the hydraulic fracturing fluid; and a static mixer
for receiving the hydraulic fracturing fluid to ensure complete
hydration of the polymer prior to fracturing the formation.
15. The mobile unit as claimed in claim 14, further comprising at
least one water filter for filtering the water prior to adding it
to the polymer.
16. The mobile unit as claimed in claim 14, further comprising a
motor control center for receiving power from a power source for
controlling the equipment on the mobile unit.
Description
[0001] This is a Continuation-in-Part of U.S. patent application
Ser. No. 12/255,478, filed Oct. 21, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
hydraulic fracturing of oil and gas wells, and, more particularly,
to a process and process line which allows for the formation of
fracturing fluid at a central location.
BACKGROUND OF THE INVENTION
[0003] Hydraulic fracturing, or fracing, is used to
initiate/stimulate oil or gas production in low-permeability
reservoirs. Hydraulic fracing has become particularly valuable in
gas reservoirs wells and has been a key factor in unlocking the
potential of unconventional gas plays, such as coal-bed methane,
tight gas and shale gas reservoirs.
[0004] In hydraulic fracing, a fluid is injected into a well at
such high pressures that the structure "cracks", or fractures.
Fracing is used both to open up fractures already present in the
formation and to create new fractures. These fractures permit
hydrocarbons and other fluids to flow more freely into or out of
the well bore. Desirable properties of a hydraulic fracturing fluid
may include high viscosity, low fluid loss, low friction during
pumping into the well, stability under the conditions of use such
as high temperature deep wells, and ease of removal from the
fracture and well after the operation is completed.
[0005] Slick Water fracs have become more common, as they tend to
be the least expensive of the fracture fluids. As part of the frac
procedure, propping agents, or proppants, are often injected along
with the fluid to "prop" open the new fractures and keep the cracks
open when fracturing fluid is withdrawn. Hybrid fracs which are a
combination of slick water and conventional frac technology are
also becoming popular. A number of different proppants can be used
such as sand grains, ceramics, sintered bauxite, glass or plastic
beads, or other material. Thus, it is also important that the
fracturing fluid be able to transport large amounts of proppant
into the fracture.
[0006] Depending on the particular fracing operation, it may be
necessary that the fluid be viscosified to help create the fracture
in the reservoir and to carry the proppant into this fracture. In
Hybrid fracs, crosslinkers could be added at the frac site, as the
viscosity would be too high to pump through a pipeline. The high
gel loading for non crosslinked Hybrid fracs would require that
additional polymer be added at the frac site. Thus, water-based
fracing fluids often include friction reducing polymers and/or
viscosifiers such as polyacrylamides and polymethacrylamides,
cross-linked polyacrylamides and cross-linked polymethacrylamides,
polyacrylic acid and polymethacrylic acid, polyacrylates, polymers
of N-substituted acrylamides, co-polymers of acrylamide with
another ethylenically unsaturated monomer co-polymerizable
therewith, 2-acrylamido-2-methylpropane sulfonic acid, polyvinyl
pyrollidones, guar, substituted guars, other biopolymers such as
xanthan such as xanthan gum, welan gum and diutan gum, derivatized
biopolymers such as carboxymethyl cellulose, and other mixtures of
polymers. Other chemicals such as scale inhibitor to prevent
scaling, oxygen scavengers, H.sub.2S scavengers, biocides, and the
like, may also be added.
[0007] It was common practice in the industry at one time to batch
mix fracturing fluids at the well site. This was very costly and
dependent upon water being present or being transported to remote
sites and the bags of polymer, chemicals, etc. being transported on
site. Further, incomplete mixing of the polymer and water was also
a problem. If the dispersion of the polymer is incomplete, clumps
of partially hydrated polymer can form, which clumps are commonly
referred to in the industry as "fisheyes".
[0008] More recently, liquid polymers, such as DynaFrac.TM. HT
fluids, are being brought to the well site. However, the price of
the premixed polymer itself and the costs to transport these large
totes of liquid polymer make this a very costly alternative.
[0009] The present invention addresses these problems and provides
a more cost effective process for preparing hydraulic fracturing
fluid.
SUMMARY OF THE INVENTION
[0010] In an aspect of the present invention, a process is provided
for preparing a friction-reduced hydraulic fracturing fluid at a
central location which can be readily transported to an oil or gas
well in a formation at a well site, comprising: [0011] preparing a
mixture of polymer and water at the central location by shearing
the polymer in the mix water in a high shear environment to create
the friction-reduced hydraulic fracturing fluid; [0012] pumping the
friction-reduced hydraulic fracturing fluid through a series of
pumps and pipelines to the well site; and [0013] injecting the
hydraulic fracturing fluid into the gas well at a pressure
sufficient to cause fracturing of the formation.
[0014] In one embodiment, additional water is added to the pumps to
further dilute the friction-reduced hydraulic fracturing fluid.
[0015] In one embodiment, additives such as surfactants, acid,
biocides, oxygen scavengers, H.sub.2S scavengers, scale inhibitors
and the like are added to the water or the sheared friction-reduced
hydraulic fracturing fluid prior to pumping it to the remote well
site.
[0016] In another embodiment, the friction-reduced hydraulic
fracturing fluid is retained in a surge tank at the remote well
site prior to pumping it down the gas well. In another embodiment,
a blender is provided at the well site for mixing proppant such as
sand with the friction-reduced hydraulic fracturing fluid.
[0017] In another aspect of the present invention, a process line
is provided, comprising: [0018] a water plant site having: [0019] a
water supply; [0020] a bulk polymer storage tank containing a
supply of polymer; [0021] a shearing mixer operably associated with
both the bulk polymer storage tank and the water supply for
receiving the polymer and mixing the polymer with sufficient water
to form a friction-reduced hydraulic fracturing fluid; [0022] at
least one pump for pumping the friction-reduced hydraulic
fracturing fluid though at least one pipeline to a well site; and
[0023] at least one fracturing pump located at the remote well site
for receiving the hydraulic fluid/proppant mixture and pumping it
down at least one gas well located at the well site.
[0024] In one embodiment, the process line further comprises a
blender located at the remote site and operably associated with the
at least one pipeline for receiving the friction-reduced hydraulic
fracturing fluid and mixing it with a portion of a proppant.
[0025] In another embodiment, the process line comprises at least
two pumps for pumping the friction-reduced hydraulic fracturing
fluid through the at least one pipeline. In this embodiment, one
could optionally provide a static mixer between the at least two
pumps. The addition of the static mixer is to ensure thorough
mixing of the polymer and water to prevent the formation of
fisheyes. Studies have also shown that fisheyes and/or "microgels"
present in some polymer gelled carrier fluids will plug pore
throats, causing formation damage.
[0026] In another aspect of the present invention, a mobile
hydraulic fracturing fluid preparation unit for preparing hydraulic
fracturing fluid at a well site is provided, comprising: [0027] a
mobile trailer having a plurality of wheels or a skid and further
having: [0028] a shearing mixer for receiving a polymer from a bulk
polymer storage tank and for receiving water from a water source
and operable to mix the polymer with sufficient water to hydrate
the polymer, and [0029] at least one pump for receiving the
hydrated polymer and for receiving additional water from the water
source to form the hydraulic fracturing fluid and for pumping the
hydraulic fracturing fluid to at least one frac pump located at the
well site, the at least one frac pump operable to deliver the
hydraulic fracturing fluid to an oil or gas well located at the
well site at a sufficient pressure to fracture the formation
surrounding the well.
[0030] It is understood by those skilled in the art that a frac
pump is a high-pressure, high-volume pump used in hydraulic
fracturing treatments.
[0031] The shearing mixer can be any high-speed blender capable of
rapidly dispersing (shearing) the polymer throughout the mix
water.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Referring to the drawings wherein like reference numerals
indicate similar parts throughout the several views, several
aspects of the present invention are illustrated by way of example,
and not by way of limitation, in detail in the figures,
wherein:
[0033] FIG. 1 is a schematic of a process line as per one
embodiment of the present invention;
[0034] FIG. 2 is a schematic of a shearing mixer useful in the
present invention; and
[0035] FIG. 3 is a schematic of an embodiment of a mobile hydraulic
fracturing fluid preparation unit.
DESCRIPTION OF PREFERRED EMBODIMENT
[0036] The detailed description set forth below in connection with
the appended drawings is intended as a description of one of the
embodiments of the present invention and is not intended to
represent the only embodiments contemplated by the inventors. The
detailed description includes specific details for the purpose of
providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the
present invention may be practiced without these specific
details.
[0037] The present invention, both as to its organization and
manner of operation, may best be understood by reference to the
following description and the drawings wherein numbers are used
throughout several views to label like parts. Certain parts which
are mentioned may be absent in particular figures due to the view
of the drawing or obstruction by other parts.
[0038] An embodiment of a process line of the present invention is
illustrated in FIG. 1. The process line is generally divided into
two main areas, water plant site 10 and remote well site 30.
Turning first to water plant site 10, water is supplied to water
plant site 10 from source wells 18 and optionally the water is
filtered through a water filtering unit 20. It is understood,
however, that in addition to freshwater or saline wells, any water
source such as recycled water, a river, lake, ocean and the like
can be used. Optionally, water filtering unit 20, for example, a
commercial reverse osmosis water filter such as a filter
manufactured by RainDance.TM. Water Systems LLC, can be used to
reduce the total dissolved solids. In addition, reverse osmosis
filters can also be designed for removal of sodium salts
(desalination), bacteria, silica, sulfates, H.sub.2S, etc. In the
alternative, cyclone filters known in the art can be used. The
water filtering unit 20 can act also act as a water storage tank
itself or, in the alternative, a separate water storage tank can be
provided (not shown). In one embodiment, the water storage tank is
heated. Depending upon the quality of water from the water source
delivers water, it may be possible to directly use the water
without the need to filter or store the water.
[0039] A larger polymer storage tank 12 is also provided at the
water plant site, which storage tank is preferably large enough to
hold about 20 metric tonnes of polymer or more. Polymers useful in
the present embodiment include friction reducing polymers such as
partially hydrolyzed polyacrylamides, polyacrylamides and
polymethacrylamides, cross-linked polyacrylamides and cross-linked
polymethacrylamides, polyacrylic acid and polymethacrylic acid,
polyacrylates, polymers of N-substituted acrylamides, co-polymers
of acrylamide with another ethylenically unsaturated monomer
co-polymerizable therewith, 2-acrylamido-2-methylpropane sulfonic
acid, polyvinyl pyrollidones, biopolymers such as xanthan, guars,
derivitized guars, derivitized cellulose and other mixtures of
polymers. Near the bottom of the polymer storage tank 12 is an
auger or conveyer 14, which auger/conveyer 14 may be controlled by
a control panel (not shown) at the water plant site 10.
[0040] The auger/conveyer 14 delivers an appropriate amount of
polymer to high shear mixer 16. Water is also delivered to mixer 16
via pipe 22, which pipe 22 is connected to water filtering unit 20
via outlet pipe 21. The high shear mixer 16 can be any one of many
high shear mixers known in the art which are capable of shearing a
solid polymer with water. Useful high shear mixers generally
comprise sharp blades or impellers, which blades or impellers are
capable of rotating at very high speeds, for example, in excess of
40,000 rmp. An example of a high shear mixer useful in the present
embodiment is an Urschel Laboratories Incorporated Comitrol.RTM.
Processor Model 1700. It is understood, however, that other mixing
vessels or mixing devices known in the art can also be used.
[0041] An embodiment of a high shear mixer useful in the present
invention is shown in more detail in FIG. 2. In this embodiment,
high shear mixer 216 comprises hopper 270 for receiving polymer
from the polymer storage tank. Water is added to hopper 270 for
mixing with the polymer as well as for washing the impellers 274
contained in shear box 272. The sheared polymer/water mixture is
then contained in holding vessel 276 prior to being removed from
outlet 278 via a pump, such as pump 26 in FIG. 1.
[0042] Additional water may be added to the polymer/water mixture
via pipe 24 while the polymer/water mixture is being pumped through
pump 26 to form dilute hydraulic fracturing fluid having reduced
friction. The ratio of polymer to water will be dependent upon the
geophysical characteristics of a particular reservoir or formation.
For example, in some instances, very little polymer will be added
to the water, for example, when used for fracturing shale (low
rate) wells. Sometimes, no polymer needs to be added at all. In
this instance, valve 23 is shut off and instead only valve 25 is
opened. In this instance, only pure water will be pumped to remote
well site 30. Thus, in the present invention, the friction-reduced
hydraulic fracturing fluid has a viscosity in the range of about 1
to about 15000 cP, more preferably about 1 to about 100 cp, and
most preferably about 1 to about 20 cP. However, during a Hybrid
frac some chemicals such as additional polymers and/or a cross
linker are required to be added at the well site.
[0043] Additional chemicals can be added to the high shear mixture,
for example, a scale inhibitor component to prevent scaling, oxygen
scavengers, H.sub.2S scavengers, biocides, surfactants, caustic
soda, antifoaming agents, iron chelators, and the like at pump 26.
This can be added before or after the polymer. Once the polymer and
water are sufficiently mixed, a "slippery" hydraulic fracturing
fluid having reduced friction is formed. In one embodiment, an
in-line static mixer is provided between pump 26 and another pump
28 to ensure that the polymer is completely hydrated. The reduced
friction fracturing fluid can now be readily pumped through
pipeline 29 to remote well site 30.
[0044] Remote well site 30 comprises a plurality of oil or gas
wells 32 into which hydraulic fracturing fluid needs to be
delivered. The hydraulic fracturing fluid can be stored for a
period of time in surge tank 34 until fracturing operations begin.
When fracturing operations begin, the fracturing fluid is
optionally mixed with a proppant 36 such as sand grains, ceramics,
sintered bauxite, glass or plastic beads, or other material, in a
blender 38. The proppant blended hydraulic fracturing fluid can
then be transported via piping 42 to a plurality of individual Hp
pumps to the plurality of gas wells 32.
[0045] As previously mentioned, liquid polymer (hydraulic
fracturing fluid) is normally transported directly to the remote
well site. Thus, there are many expenses associated with
transporting polymer and water to such remote sites. Further,
addition of any other chemicals must also take place at the remote
well site, hence, added to the costs are the costs associated with
transporting these chemicals to these remote places. However, the
embodiment of the invention as described above is much more cost
effective, as the hydraulic fracturing fluid is made entirely at a
central water plant site, which central site can then service a
number of remote well sites simultaneously.
[0046] In another aspect of the present invention, an improved
mobile hydraulic fracturing fluid unit is provided, which unit is
designed to make hydraulic fracturing fluid directly at the well
site without at least one of the previously discussed drawbacks,
for example, the formation of fisheyes and the like. With reference
now to FIG. 3, mobile hydraulic fracturing fluid unit 300 comprises
a mobile trailer or skid 301 having a plurality of wheels or the
like so that the unit can be easily transported to a remote well
site. Already present at the remote well site is bulk polymer
storage tank 312 and water source 318. Depending upon the water
source, the water can be used either directly or treated prior to
use.
[0047] In the embodiment shown in FIG. 3, unit 300 comprises a
first water filter 320 and a second water filter 320'. Filtered or
non-filtered water or both can then be delivered to shearing mixer
216 or pump 326 or both. To ensure complete mixing/hydration of the
polymer with water, the polymer/water is pumped via pump 326 into
in-line static mixer 327. It is understood that any static mixer
known in the art can be used. Unit 300 also comprises motor control
center (MCC) 331, which is designed to control some motors or all
the motors of unit 300 from a central location, namely, remote
power source 333, which power can be supplied by Hi Line (i.e.,
power right to the site off of the power line) or Gen Set (i.e.,
generator). Polymer is delivered to shearing mixer 316 from bulk
polymer storage tank 312 via conveyer/auger 314. As shown in FIG.
1, once the hydraulic fracturing fluid is made, it can optionally
be pumped to a blender where proppant can be added, if needed.
[0048] The previous description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
present invention. Various modifications to those embodiments will
be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the present invention is not intended to be limited to the
embodiments shown herein, but is to be accorded the full scope
consistent with the claims, wherein reference to an element in the
singular, such as by use of the article "a" or "an" is not intended
to mean "one and only one" unless specifically so stated, but
rather "one or more". All structural and functional equivalents to
the elements of the various embodiments described throughout the
disclosure that are known or later come to be known to those of
ordinary skill in the art are intended to be encompassed by the
elements of the claims. Moreover, nothing disclosed herein is
intended to be dedicated to the public regardless of whether such
disclosure is explicitly recited in the claims.
* * * * *